lpg performance
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From: Daryl Walford on 30 Aug 2007 01:21 Ron wrote: > "Jason James" <at(a)peace.com> wrote in > news:46d56fee$0$15512$c30e37c6(a)pit-reader.telstra.net: > >> "Paul Saccani" <saccani(a)omen.net.au> wrote in message >> news:lvpad39vevt1g2gcf6tgcgfn8k56vu9f6l(a)4ax.com... >>> On 29 Aug 2007 09:34:24 GMT, Ron <dodo(a)hotmail> wrote: >>> >>>> motoxxx43(a)hotmail.com wrote in news:1188375500.446790.194600 >>>> @q3g2000prf.googlegroups.com: >>>> >>>>> hi i have recently have had my toyota 4runner converted to lpg and >>>>> have loss significant amount of power and was wondering if this is >>>>> just normal for gas and if so what sort of engine mods work good >>>>> with lpg? any info on this wold be greatly appreciated thnks >>>>> >>>>> >>>> Tuning, you may have to retard the ignition >>> It's the other way around - you advance the spark curve at low RPM, >>> and retard the high end *compared* with a petrol curve at high RPM by >>> as much advance as you added at low RPM. >>> >>> This used to be done by distributor modifications, but it hard to get >>> these done nowadays, so you could use something like an AEB >>> "Electronic Spark Advance Variator", which comes in a range of models >>> to suit different kinds of ignition systems. Besides being easier >>> to set up, it runs dual curves, one for Petrol and one for LPG. >>> >>>> and increase the gas flow. >>>> It will use more gas, but it is cheaper :-) >> The theory is, as far as I can dtermine, that LPG/air burns slower >> than petrol-mist/air, and hence this imparts a higher octane rating. >> The Cleveland 5.8L I have on gas will not ping with quite high >> advances up to 50 degrees BTDC. Hasten to add I didnt leave it like >> that, the "HEI" dizzy I bought new was set-up that way initially. This >> engine also has a significant power drop on gas, and after much >> investigation including a wide range of inneffective mixture and >> ignition timing settings, Athol who is an engineer here, passed the >> opinion that its likely the "mixer" is too small and is limiting >> intake. The carter carby has quite high CFM figures, but opening the >> secondaries doesnt alter engine output, or more significantly, doesnt >> cause a mixture change, hence the open secs are only acting as a >> larger intake manifold 'mouth' size without any chnage in flow thru >> the mixer on top, as its already maxed-out. Not saying this is the OP >> problem, but thought it worth mentioning. >> >> Jason > > With the XJ6, the timing has to be changed from 6 BTDC to 12, otherwise > it gets very hot :-) In other words you have advanced it 6 deg which is what is normally done. Daryl
From: Ron on 30 Aug 2007 01:25 John McKenzie <jmac_melbourne(a)bigpond.com> wrote in news:46D6466D.441B(a)bigpond.com: >> With the XJ6, the timing has to be changed from 6 BTDC to 12, otherwise >> it gets very hot :-) > > Which makes perfect sense Ron, but the problem is that at higher rpms, > once the mechnical advance comes in, it will be 6 degrees more advanced > at the higher rpms (for any given rpm point, in effect it'll be 6 > degrees more advanced). > > Now that _is_ generally what you would want and need up to about > 2500-2600rpm (possibly 3000rpm, but I'd want to look at the factory > curve, and for that matter the dizzy period, as the advance springs > would have almost definitely have sagged altering the scenario too). > > What you might actually find is that the springs _have_ sagged, and when > you adjust it to 12 initial, the mech advance has already come in > somewhat due to sagged springs and it might therefore actually not have > more advance up higher than if you had setup a brand new stock curved > dizzy in there. > > So in that instance, you might actually have lucked into a situation > where running 12 degrees initial _was_ alright all round for lpg. I > wouldn't bet on it, but it's certainly not inconceivable given the > circumstances as I've inferred/interpreted them to be. > John, That is indeed possible, the distributor is 33 years old :-) 3000rpm is as high as I ever take it, and it runs out of power at 4000. Recently I had it on initial of 8BTDC and the car ran out of puff at 3000rpm. If you kicked it back to 2nd at 100kph, nothing happened, it could not gain speed :-) It never used to be like that, so I guess I should take it to a LPG joint and get it tuned. Perhaps I should overhaul the dizzy first:-) Cheers, Ron
From: Daryl Walford on 30 Aug 2007 01:26 John McKenzie wrote: > Jason James wrote: >> >> Yeah, I'm starting to think, earlier conversions (mine was in '99) were less >> than optimum in many cases. Sensitivity to ignition advance seems to vary >> radically from engine to engine on gas. The Clevo needs very fast ignition >> advance to quite high figures to put out any sort of power. > > Which interestingly enough (well at least the fact that it likes it up > higher) is good evidence that the lpg mixer isn't able to flow enough. > > You're basically running a restrictor plate engine of sorts! > > Too small a convertor is a common enough problem. A mate bought a Mazda E2000 van new and converted it to LPG, for years it was gutless on gas and seemed to use too much gas. When the van was about 5 yrs old the convertor failed, he took it to a gas specialist who took one look at the old convertor and said he was surprised the engine ran at all, after fitting a new convertor of the correct capacity it was like a new vehicle, performance improved as did economy. Daryl
From: Ron on 30 Aug 2007 02:07 Daryl Walford <dwalford(a)internode.on.net> wrote in news:13dckqs4srfs890 @corp.supernews.com: > Ron wrote: >> "Noddy" <dg4163@(nospam)dodo.com.au> wrote in >> news:46d54e7d$0$90162$c30e37c6(a)lon-reader.news.telstra.net: >> >>> "Ron" <dodo(a)hotmail> wrote in message >>> news:Xns999BC82D95BE4GPS(a)64.209.0.82... >>> >>>> Tuning, you may have to retard the ignition and increase the gas >>>> flow. It will use more gas, but it is cheaper :-) >>> Don't do that :) >>> >>> Retarding the timing will only make it worse unless it's got way too >>> much advance now, and you'd notice that on petrol if it did. >>> >>> Tuning gas systems is like tuning anything else in that there's >>> different types of systems than each have their own peculiarities and >>> need special attention to suit. There shouldn't be anything other than >>> a mildy noticable power difference between gas & petrol on a dual fuel >>> system, but if there is then you need to get it back to the gas fitter >>> and have them tune it *properly*. >>> >>> That's what you paid them for. >> >> Noddy, >> >> The XJ6 has a OMVL R90e. >> The ignition timing for LPG has to be altered or the car overheats. >> > Are you sure its retarded from standard? > The normal practice is to advance engines running on gas, the standard > advance on the XD Van I had is 6deg, it was set at 15 deg when I bought > it and I didn't change it and it always ran well. > One of the tricks electronic engine management uses when an engine > overheats is to advance the timing so I'm surprised if yours is the > opposite. Daryl The guy that fitted it, changed the setting. Normal (static) is 6BTDC and he said run it on 12, so I don't know :-)
From: Ron on 30 Aug 2007 02:09
Daryl Walford <dwalford(a)internode.on.net> wrote in news:13dckuhs1igtjf0 @corp.supernews.com: > Ron wrote: >> "Jason James" <at(a)peace.com> wrote in >> news:46d56fee$0$15512$c30e37c6(a)pit-reader.telstra.net: >> >>> "Paul Saccani" <saccani(a)omen.net.au> wrote in message >>> news:lvpad39vevt1g2gcf6tgcgfn8k56vu9f6l(a)4ax.com... >>>> On 29 Aug 2007 09:34:24 GMT, Ron <dodo(a)hotmail> wrote: >>>> >>>>> motoxxx43(a)hotmail.com wrote in news:1188375500.446790.194600 >>>>> @q3g2000prf.googlegroups.com: >>>>> >>>>>> hi i have recently have had my toyota 4runner converted to lpg and >>>>>> have loss significant amount of power and was wondering if this is >>>>>> just normal for gas and if so what sort of engine mods work good >>>>>> with lpg? any info on this wold be greatly appreciated thnks >>>>>> >>>>>> >>>>> Tuning, you may have to retard the ignition >>>> It's the other way around - you advance the spark curve at low RPM, >>>> and retard the high end *compared* with a petrol curve at high RPM by >>>> as much advance as you added at low RPM. >>>> >>>> This used to be done by distributor modifications, but it hard to get >>>> these done nowadays, so you could use something like an AEB >>>> "Electronic Spark Advance Variator", which comes in a range of models >>>> to suit different kinds of ignition systems. Besides being easier >>>> to set up, it runs dual curves, one for Petrol and one for LPG. >>>> >>>>> and increase the gas flow. >>>>> It will use more gas, but it is cheaper :-) >>> The theory is, as far as I can dtermine, that LPG/air burns slower >>> than petrol-mist/air, and hence this imparts a higher octane rating. >>> The Cleveland 5.8L I have on gas will not ping with quite high >>> advances up to 50 degrees BTDC. Hasten to add I didnt leave it like >>> that, the "HEI" dizzy I bought new was set-up that way initially. This >>> engine also has a significant power drop on gas, and after much >>> investigation including a wide range of inneffective mixture and >>> ignition timing settings, Athol who is an engineer here, passed the >>> opinion that its likely the "mixer" is too small and is limiting >>> intake. The carter carby has quite high CFM figures, but opening the >>> secondaries doesnt alter engine output, or more significantly, doesnt >>> cause a mixture change, hence the open secs are only acting as a >>> larger intake manifold 'mouth' size without any chnage in flow thru >>> the mixer on top, as its already maxed-out. Not saying this is the OP >>> problem, but thought it worth mentioning. >>> >>> Jason >> >> With the XJ6, the timing has to be changed from 6 BTDC to 12, otherwise >> it gets very hot :-) > > In other words you have advanced it 6 deg which is what is normally done. > > > Daryl > Is going from 6BTDC to 12 BTDC advancing? I would have thought that is retarding the spark? |